U.S. patent application number 14/737410 was filed with the patent office on 2015-12-17 for optical acquisition device for biometric systems.
The applicant listed for this patent is MORPHO. Invention is credited to Sylvaine Picard, Francois Rieul.
Application Number | 20150365589 14/737410 |
Document ID | / |
Family ID | 51610247 |
Filed Date | 2015-12-17 |
United States Patent
Application |
20150365589 |
Kind Code |
A1 |
Rieul; Francois ; et
al. |
December 17, 2015 |
OPTICAL ACQUISITION DEVICE FOR BIOMETRIC SYSTEMS
Abstract
The invention relates to a device for acquisition of images for
a biometric system, which includes an optical assembly and at least
one imager for acquisition of an image of an object to be analysed
presented in front of the assembly at a non-determined distance
from the latter. The assembly includes at least one diaphragm with
a coded aperture. The optical assembly allows acquisition by the
sensor(s) of an image of the object capable of being exploited to
deduce therefrom the searched biometric information, and of an
image of the object acquired via the coded aperture of the
diaphragm. The device also includes a processing unit to determine
the distance of the object to be analysed as a function of the
image of the object acquired via the coded aperture of the
diaphragm.
Inventors: |
Rieul; Francois; (Issy Les
Moulineaux, FR) ; Picard; Sylvaine; (Issy Les
Moulineaux, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MORPHO |
Issy-Les-Moulineaux |
|
FR |
|
|
Family ID: |
51610247 |
Appl. No.: |
14/737410 |
Filed: |
June 11, 2015 |
Current U.S.
Class: |
348/77 |
Current CPC
Class: |
A61B 5/1171 20160201;
A61B 5/117 20130101; G06T 7/50 20170101; G06T 2207/30196 20130101;
H04N 5/23212 20130101; H04N 5/23218 20180801; H04N 5/23219
20130101; G06K 9/00597 20130101; A61B 3/14 20130101 |
International
Class: |
H04N 5/232 20060101
H04N005/232; H04N 5/225 20060101 H04N005/225; G06K 9/00 20060101
G06K009/00; G06T 7/00 20060101 G06T007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 13, 2014 |
FR |
1455447 |
Claims
1. A device for acquisition of images for a biometric system,
comprising an optical assembly and at least one imager for
acquisition of an image of an object to be analysed presented in
front of said assembly at a non-determined distance from the
latter, wherein it comprises at least one diaphragm with coded
aperture, the optical assembly being adapted to allow acquisition
by the sensor(s): on one hand, of an image of the object capable of
being exploited to deduce therefrom the searched biometric
information, and on the other hand, of an image of the object
acquired via the coded aperture of a diaphragm, said device further
comprising a processing unit adapted to determine the distance of
the object to be analysed as a function of the image of the object
acquired via the coded aperture of said diaphragm.
2. The device according to claim 1, wherein the image of the object
acquired via the coded aperture serving to determine the distance
is acquired in one or more frequency bands separated from the work
frequency band(s) used for acquisition of the image carrying the
searched biometric information.
3. The device according to claim 2, wherein the optical assembly
comprises two colour filters, one transmitting in the work
frequency band used for acquisition of the image carrying the
searched biometric information, the other transmitting in another
frequency band, at least one of these two filters bearing a
diaphragm with coded aperture.
4. The device according to claim 3, wherein the filters are made in
a stack.
5. The device according to claim 2, wherein it comprises lighting
capable of projecting onto the object observed an image in the
frequency band used for the diaphragm with coded aperture.
6. The device according to claim 2, wherein the frequency band of
the diaphragm with coded aperture is in the blue field.
7. The device according to claim 2, wherein the optical assembly
comprises at least two diaphragms: one diaphragm used for
acquisition of the image carrying the searched biometric
information, said diaphragm being fitted with: an aperture (O)
transparent at least to work wavelengths (.lamda.w), to wavelengths
(.lamda.d) for determining the distance of a semi-opaque surface
being: opaque to work wavelengths (.lamda.w), and transparent to
wavelengths (.lamda.d) for determining the distance, and said work
wavelengths (.lamda.w) and wavelengths (.lamda.d) for determining
the distance being separate wavelengths, a second diaphragm with
coded aperture used for acquisition of the information for
determining the distance, said diaphragm being fitted with: a
semi-opaque surface: opaque to wavelengths (.lamda.d) for
determining the distance, and transparent to work wavelengths
(.lamda.w), and a coded aperture (OC) transparent to work
wavelengths (.lamda.w), and to wavelengths (.lamda.d) for
determining the distance.
8. The device according to claim 2, wherein the aperture (O) of the
diaphragm is a centred and circular aperture enabling acquisition
of an image of high quality of the object in the work wavelengths
(.lamda.w).
9. The device according to claim 2, wherein the aperture (O) of the
diaphragm is a coded aperture separate from the coded aperture (OC)
of the diaphragm, the image of the object being reconstituted from
information acquired at the outlet of the two diaphragms.
10. The device according to claim 2, wherein the optical assembly
comprises a beam splitter sending back to two separate imagers an
image of the object in different frequency bands, one being one or
more work frequency bands used for acquisition of the image
carrying the searched biometric information, the other being one or
other frequency bands, a centred diaphragm being arranged in front
of the imager receiving the image in the work frequency band, the
diaphragm with coded aperture being arranged in front of the other
imager.
11. Use of a device according to claim 1 for acquisition of "OTF"
biometric images.
12. Use of a device according to claim 1 for identification or
authentication by facial recognition and/or iris acquisition and/or
fingerprint acquisition and/or venous image acquisition.
Description
GENERAL TECHNICAL FIELD AND PRIOR ART
[0001] The present invention relates to .optical acquisition in
biometric systems.
[0002] It applies particularly advantageously to biometric systems
using acquisition of images on the fly ("OTF" or "On The Fly" as
per English terminology in general use), for example for
identification or authentication by facial recognition, iris
acquisition, fingerprint acquisition or venous image acquisition,
etc. Biometric systems conventionally endeavour to know the
distance separating the object from the camera, which enables:
[0003] deconvoluting with appropriate deconvolution filter, and
therefore canceling blurring;
[0004] activating focusing systems,
[0005] knowing the resolution at which the object is being
observed.
[0006] The knowledge of this distance is often obtained by
projection of a sight and by triangulation between the latter and
the sight lines occurring with formation of images. This method is
highly efficacious but has the disadvantage of being fairly bulky
and disrupting the resulting image by the presence of the
sight.
[0007] Minimum parallax between the sight and the camera is needed
and consequently a certain hindsight.
[0008] It is further costly in terms of additional optics and
electronics.
[0009] It is also already known in optics to use coded apertures on
cameras for determining the distance from the object being
observed.
[0010] Reference could be made for example in this respect to the
following articles:
[0011] Zhou Et Nayar "Coded Aperture Pairs for Depth from Defocus",
2009 -Extended version: International Journal of Computer Vision,
May 2011, Volume 93, Issue 1, pp 53-72
[0012] Levin et al. "Image and Depth from a Conventional Camera
with a Coded Aperture"--ACM transactions on graphics, Vol. 26, no.
3, article 70, July 2007.
[0013] The disadvantage of the coded apertures however is that they
strongly degrade the quality of the image they produce.
[0014] They are consequently generally considered incompatible with
highly precise acquisition of images.
GENERAL PRESENTATION OF INVENTION
[0015] An aim of the invention is to eliminate the disadvantages of
techniques used to date for determining a distance from the object
in the case of biometric systems.
[0016] More precisely, the invention proposes a solution which is
inexpensive and not bulky.
[0017] For this purpose, the invention proposes using diaphragms
with a coded aperture in biometric systems.
[0018] Diaphragm with coded aperture here and throughout the
present text means any diaphragm with aperture other than a centred
and circular hole, and in particular, but not limited to, any
diaphragm aperture consisting of several holes.
[0019] More precisely, the invention proposes a device for
acquisition of images for a biometric system, comprising an optical
assembly and at least one imager for the acquisition of an image of
an object to be analysed presented in front of said assembly at a
non-determined distance from the latter, characterized in that it
comprises at least one diaphragm with coded aperture, the optical
assembly being adapted to allow acquisition by the sensor(s):
[0020] on the one hand, of an image of the object capable of being
exploited to deduce therefrom the searched biometric information,
and
[0021] on the other hand, of an image of the object acquired via
the coded aperture of the diaphragm,
[0022] said device further comprising a processing unit adapted to
determine the distance of the object to be analysed as a function
of the image of the object acquired via said coded aperture of the
diaphragm.
[0023] In particular, the optical assembly is advantageously
adapted so that the image of the object acquired via the coded
aperture serving to determine the distance is acquired in one or
more frequency bands separated from the work frequency band(s) used
for acquisition of the image carrying the searched biometric
information.
[0024] Different colours are thus used for the images acquired by
the imagers, while the acquisitions of biometric images are
generally made by considering only one frequency band.
[0025] Advantageously, the optical assembly comprises two colour
filters, one transmitting in the work frequency band used for
acquisition of the image carrying the searched biometric
information, the other transmitting in another frequency band, at
least one of these two filters bearing a diaphragm with coded
aperture.
[0026] In a possible embodiment, the optical assembly comprises at
least two diaphragms:
[0027] one diaphragm used for acquisition of the image carrying the
searched biometric information, said diaphragm D being fitted with:
[0028] one aperture (O) at least transparent [0029] to work
wavelengths (.lamda.w), [0030] to wavelengths (.lamda.d) for
determining the distance [0031] a semi-opaque surface being: [0032]
opaque to work wavelengths (.lamda.w), and [0033] transparent to
wavelengths (.lamda.d) for determining the distance, and [0034]
said work wavelengths (.lamda.w) and wavelengths (.lamda.d) for
determining the distance being separate wavelengths, [0035] a
second diaphragm with coded aperture used for acquisition of
information for determining the distance, said diaphragm being
fitted with: [0036] a semi-opaque surface being: [0037] opaque to
wavelengths (.lamda.d) for determining the distance, and [0038]
transparent to work wavelengths (.lamda.w), and [0039] a coded
aperture (OC) transparent [0040] to work wavelengths (.lamda.w) and
[0041] to wavelengths (.lamda.d) for determining the distance.
[0042] According to a preferred embodiment the aperture (O) of the
diaphragm is a centred and circular aperture enabling acquisition
of an image of high quality of the object in the work wavelengths
(.lamda.w).
[0043] According to an alternative embodiment the aperture (O) of
the diaphragm D is a coded aperture separate from the coded
aperture (OC) of the diaphragm DOC, the image of the object being
reconstituted from information acquired at the outlet of the two
diaphragms.
[0044] In all cases, the apertures (O) and (OC) are equally
transparent or opaque to other wavelengths (.lamda.qc), given that
the latter are separate from the work wavelengths (.lamda.w) and
wavelengths (.lamda.d) for determining the distance.
[0045] As a variant, the optical assembly comprises a beam splitter
sending back to two separate imagers an image of the object in
different frequency bands,
[0046] one being one or more work frequency band(s) used for
acquisition of the image carrying the searched biometric
information,
[0047] the other being one or more other frequency band(s), a
centred diaphragm being arranged in front of the imager receiving
the image in the work frequency band, the diaphragm with coded
aperture being arranged in front of the other imager.
PRESENTATION OF FIGURES
[0048] Other characteristics and advantages of the invention will
emerge from the following description, which is purely illustrative
and non-limiting, and must be considered in conjunction with the
appended figures, in which:
[0049] FIG. 1 schematically illustrates an acquisition system
according to a possible embodiment for the invention;
[0050] FIG. 2 illustrates an acquisition system according to
another equally possible embodiment.
DESCRIPTION OF ONE OR MORE EMBODIMENTS
[0051] In the example illustrated in FIG. 1, the device is intended
to acquire an image of the face or iris of the eye of an individual
(object I) passing in front of said device.
[0052] Of course, it would be used in the same way as for other
biometric applications needing "OTF" acquisitions (acquisition "on
the fly" images of veins and or fingerprints, for example).
[0053] The device comprises an optic 1 and a beam splitter 2 and
two imagers or cameras 3a, 3b oriented at 90.degree. one relative
to the other and to which the images separated by the beam splitter
2 are sent back.
[0054] The camera 3a is linked to a diaphragm 4a with coded
aperture interposed between said camera and the beam splitter 2,
while the camera 3b is linked to a classic centred and circular
diaphragm 4b, interposed between said camera 3b and the beam
splitter 2.
[0055] The beam splitter 2 is for example a beam splitter which
filters colours by transmitting images in different frequency bands
to camera 3a and camera 3b.
[0056] The images transmitted to camera 3b with classic diaphragm
4b are images in a work frequency band for the relevant biometry,
that is, a frequency band which enables exploitation of images
acquired to deduce therefrom the searched biometric
information.
[0057] In the case of acquisition of images of veins or images of
irises, it is common to work in the near infrared. The work
frequency band filtered by the beam splitter 2 and transmitted to
the camera 3b will therefore be selected to be between [700 and 950
nm-]. In the case of acquisition of fingerprint images by contrast,
it is common to work on images in the blue-to-green field. For this
type of biometry, the work frequency band filtered by the beam
splitter 2 and transmitted to the camera 3b will therefore be
selected to be between [450 to 650 nm].
[0058] The images sent back to the camera 3a with coded aperture
diaphragm are as such images in another frequency band and in
particular in a frequency band which is not useful for obtaining
biometric information.
[0059] So for example, this frequency band can be in the IR and be
between [800 to 950 nm-].
[0060] The image now received by the camera 3a with coded aperture
is processed to determine the distance from which the object (the
individual I) is situated.
[0061] The camera 3b as such receives a fully exploitable image (no
information loss) for biometric analysis.
[0062] Processing of the images is carried out for example by a
single processing unit U to which the different images leaving the
cameras 3a, 3b are transmitted.
[0063] As a variant, and as illustrated in FIG. 2, the acquisition
system can comprise just a single multi-spectral camera 3. One or
more diaphragms 4 are interposed between the optic 1 and the camera
3.
[0064] This solution has the advantage of costing less than the
solution of FIG. 1.
[0065] In particular, in a possible embodiment the optical assembly
comprises both a standard diaphragm filter 4b for some colours
corresponding to at least one work frequency band for the relevant
biometry and a diaphragm filter 4a with coded aperture for other
colours for determining the distance.
[0066] The resulting different images are separated out between the
different colours channels of the camera 3 and analysed by the unit
U which:
[0067] determines the distance from the object I by way of the
images in the colours corresponding to the filter 4a;
[0068] determines the biometric information on the images in the
colours of the filter 4b, by using if needed the information on the
distance from the object obtained via the images of the filter
4a.
[0069] The filters 4a and 4b are for example coloured filters
(slides) with impressions of diaphragms (diaphragm with coded
aperture in the case of the filter 4a; centred and circular
diaphragm in the case of the filter 4b, for example).
[0070] These two filters 4a and 4b can be made in a stack and be in
the form of a single element 4.
[0071] In a preferred embodiment, since the work wavelengths
.lamda.w and wavelengths for determining the distance .lamda.d are
separate wavelengths, the filter 4b which constitutes the diaphragm
used for acquisition of the image carrying the searched biometric
information comprises an aperture O transparent at least to the
work wavelengths .lamda.w and the wavelengths .lamda.d for
determining the distance.
[0072] This aperture O is arranged in a semi-opaque surface which
is as such opaque to the work wavelengths .lamda.w, and transparent
to the wavelengths (.lamda.d) for determining the distance.
[0073] The filter 4a which constitutes the diaphragm with coded
aperture used for acquisition of information for determining the
distance comprises as such a semi-opaque surface which is opaque to
the wavelengths .lamda.d for determining the distance, and
transparent to the work wavelengths (.lamda.w). It further
comprises a coded aperture OC transparent to the work wavelengths
.lamda.w and the wavelengths .lamda.d for determining the
distance.
[0074] The aperture O of the diaphragm 4b can be a centred and
circular aperture for quality acquisition of the image of the
object in the work wavelengths .lamda.w.
[0075] According to another possible alternative embodiment, the
aperture O of the diaphragm 4b is a coded aperture separate from
the coded aperture OC of the diaphragm 4a, the image of the object
being reconstituted from information acquired at output of the two
diaphragms constituting the filters 4a, 4b.
[0076] In all cases, the apertures O and OC are equally transparent
or opaque to the other wavelengths .lamda.qc which are used neither
for quality of the image nor for determining distance. These
lengths .lamda.qc, which are separate from the work wavelengths
.lamda.w and the wavelengths .lamda.d used to determine the
distance, are variously filtered or not by the diaphragms 4a,
4b.
[0077] Many types of coded apertures are feasible, of course. Coded
apertures of the type of those proposed in the following article
could be used, for example:
[0078] Levin et al. "Image and Depth from a Conventional Camera
with a Coded Aperture"--ACM transactions on graphics, Vol. 26, no.
3, article 70, July 2007.
[0079] Calculation of distance performed by the unit U being of the
type as described in said article.
[0080] In addition, to also improve precision on distance, it is
possible to project onto the object observed an image
(sight/lighting) at the wavelength used for the filter with coded
aperture, projection being done in the axis of the camera. This
image adds frequential information missing in the image used for
determination of distance.
[0081] It is also possible to create 2 coded apertures by
well-selected colour filterings. In this case the following is
used, for example:
[0082] Zhou Et Nayar "Coded Aperture Pairs for Depth from Defocus",
2009--Extended version: International Journal of Computer Vision,
May 2011, Volume 93, Issue 1, pp 53-72.
* * * * *